WO 2007/148988 discloses a method and a furnace for crystallization of silicon for photovoltaic cells. The furnace comprises a crucible or a plurality of crucibles for containing the silicon, a heating device for heating the crucible, a heat discharging device for discharging the heat from the crucible, and a stirring device comprising an electromagnetic device supplied with an alternating current for applying an alternating electromagnetic field to the crucible.
The stirring of the silicon melt during the crystallization of the silicon is of outermost importance to remove a large amount of impurities while obtaining a unidirectional growth of the silicon. The prior art apparatus does not seem to disclose optimum stirring in order to obtain the purest silicon possible for use in photovoltaic cells.